There are more than 8,000 officers in GMP. A police force inevitably reflects the community from which it is drawn, and while the police do some screening, it certainly isn't enough, and inevitably some bad eggs get through.
I dated a Met officer for 5 years, met all his friends and there were those I would trust absolutely, and others I wouldn't trust with the petty cash.
If stopped by the police or visited by the police, I always take a photo of ID and send it to a friend. After Wayne Couzens, it's just basic common sense, and any officer who has an issue with that is fundamentally dodgy.